package org.jaronsource.framework.util;

/**
 * Static methods for translating Base64 encoded strings to byte arrays and vice-versa.
 * 
 * @author Josh Bloch
 * @version %I%, %G%
 * @see Preferences
 * @since 1.4
 */
public class Base64 {

	/**
	 * Translates the specified byte array into a Base64 string as per Preferences.put(byte[]).
	 */
	public static String byteArrayToBase64( byte[] a ) {
		return byteArrayToBase64( a, false );
	}

	/**
	 * Translates the specified byte array into an "alternate representation" Base64 string. This non-standard variant
	 * uses an alphabet that does not contain the uppercase alphabetic characters, which makes it suitable for use in
	 * situations where case-folding occurs.
	 */
	public static String byteArrayToAltBase64( byte[] a ) {
		return byteArrayToBase64( a, true );
	}

	private static String byteArrayToBase64( byte[] a, boolean alternate ) {
		int aLen = a.length;
		int numFullGroups = aLen / 3;
		int numBytesInPartialGroup = aLen - 3 * numFullGroups;
		int resultLen = 4 * ( ( aLen + 2 ) / 3 );
		StringBuffer result = new StringBuffer( resultLen );
		char[] intToAlpha = ( alternate ? intToAltBase64 : intToBase64 );

		// Translate all full groups from byte array elements to Base64
		int inCursor = 0;
		for ( int i = 0; i < numFullGroups; i++ ) {
			int byte0 = a[inCursor++] & 0xff;
			int byte1 = a[inCursor++] & 0xff;
			int byte2 = a[inCursor++] & 0xff;
			result.append( intToAlpha[byte0 >> 2] );
			result.append( intToAlpha[ ( byte0 << 4 ) & 0x3f | ( byte1 >> 4 )] );
			result.append( intToAlpha[ ( byte1 << 2 ) & 0x3f | ( byte2 >> 6 )] );
			result.append( intToAlpha[byte2 & 0x3f] );
		}

		// Translate partial group if present
		if ( numBytesInPartialGroup != 0 ) {
			int byte0 = a[inCursor++] & 0xff;
			result.append( intToAlpha[byte0 >> 2] );
			if ( numBytesInPartialGroup == 1 ) {
				result.append( intToAlpha[ ( byte0 << 4 ) & 0x3f] );
				result.append( "==" );
			}
			else {
				// assert numBytesInPartialGroup == 2;
				int byte1 = a[inCursor++] & 0xff;
				result.append( intToAlpha[ ( byte0 << 4 ) & 0x3f | ( byte1 >> 4 )] );
				result.append( intToAlpha[ ( byte1 << 2 ) & 0x3f] );
				result.append( '=' );
			}
		}
		// assert inCursor == a.length;
		// assert result.length() == resultLen;
		return result.toString();
	}

	/**
	 * This array is a lookup table that translates 6-bit positive integer index values into their "Base64 Alphabet"
	 * equivalents as specified in Table 1 of RFC 2045.
	 */
	private static final char intToBase64[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' };

	/**
	 * This array is a lookup table that translates 6-bit positive integer index values into their
	 * "Alternate Base64 Alphabet" equivalents. This is NOT the real Base64 Alphabet as per in Table 1 of RFC 2045. This
	 * alternate alphabet does not use the capital letters. It is designed for use in environments where "case folding"
	 * occurs.
	 */
	/*
	 * private static final char intToAltBase64[] = { 'A', 'B', 'C', 'D', 'E',
	 * 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'a', 'b', 'c', 'd', 'e', 'f',
	 * 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
	 * 'u', 'v', 'w', 'x', 'y', 'z', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U',
	 * 'V', 'W', 'X', 'Y', 'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8',
	 * '9', '+', '/' };
	 */

	private static final char intToAltBase64[] = { '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':', ';', '<', '>', '@', '[', ']', '^', '`', '_', '{', '|', '}', '~', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '?' };

	/**
	 * Translates the specified Base64 string (as per Preferences.get(byte[])) into a byte array.
	 * 
	 * @throw IllegalArgumentException if <tt>s</tt> is not a valid Base64 string.
	 */
	public static byte[] base64ToByteArray( String s ) {
		return base64ToByteArray( s, false );
	}

	/**
	 * Translates the specified "alternate representation" Base64 string into a byte array.
	 * 
	 * @throw IllegalArgumentException or ArrayOutOfBoundsException if <tt>s</tt> is not a valid alternate
	 *        representation Base64 string.
	 */
	public static byte[] altBase64ToByteArray( String s ) {
		return base64ToByteArray( s, true );
	}

	private static byte[] base64ToByteArray( String s, boolean alternate ) {
		byte[] alphaToInt = ( alternate ? altBase64ToInt : base64ToInt );
		int sLen = s.length();
		int numGroups = sLen / 4;
		if ( 4 * numGroups != sLen ) throw new IllegalArgumentException( "String length must be a multiple of four." );
		int missingBytesInLastGroup = 0;
		int numFullGroups = numGroups;
		if ( sLen != 0 ) {
			if ( s.charAt( sLen - 1 ) == '=' ) {
				missingBytesInLastGroup++;
				numFullGroups--;
			}
			if ( s.charAt( sLen - 2 ) == '=' ) missingBytesInLastGroup++;
		}
		byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];

		// Translate all full groups from base64 to byte array elements
		int inCursor = 0, outCursor = 0;
		for ( int i = 0; i < numFullGroups; i++ ) {
			int ch0 = base64toInt( s.charAt( inCursor++ ), alphaToInt );
			int ch1 = base64toInt( s.charAt( inCursor++ ), alphaToInt );
			int ch2 = base64toInt( s.charAt( inCursor++ ), alphaToInt );
			int ch3 = base64toInt( s.charAt( inCursor++ ), alphaToInt );
			result[outCursor++] = (byte) ( ( ch0 << 2 ) | ( ch1 >> 4 ) );
			result[outCursor++] = (byte) ( ( ch1 << 4 ) | ( ch2 >> 2 ) );
			result[outCursor++] = (byte) ( ( ch2 << 6 ) | ch3 );
		}

		// Translate partial group, if present
		if ( missingBytesInLastGroup != 0 ) {
			int ch0 = base64toInt( s.charAt( inCursor++ ), alphaToInt );
			int ch1 = base64toInt( s.charAt( inCursor++ ), alphaToInt );
			result[outCursor++] = (byte) ( ( ch0 << 2 ) | ( ch1 >> 4 ) );

			if ( missingBytesInLastGroup == 1 ) {
				int ch2 = base64toInt( s.charAt( inCursor++ ), alphaToInt );
				result[outCursor++] = (byte) ( ( ch1 << 4 ) | ( ch2 >> 2 ) );
			}
		}
		// assert inCursor == s.length()-missingBytesInLastGroup;
		// assert outCursor == result.length;
		return result;
	}

	/**
	 * Translates the specified character, which is assumed to be in the "Base 64 Alphabet" into its equivalent 6-bit
	 * positive integer.
	 * 
	 * @throw IllegalArgumentException or ArrayOutOfBoundsException if c is not in the Base64 Alphabet.
	 */
	private static int base64toInt( char c, byte[] alphaToInt ) {
		int result = alphaToInt[c];
		if ( result < 0 ) throw new IllegalArgumentException( "Illegal character " + c );
		return result;
	}

	/**
	 * This array is a lookup table that translates unicode characters drawn from the "Base64 Alphabet" (as specified in
	 * Table 1 of RFC 2045) into their 6-bit positive integer equivalents. Characters that are not in the Base64
	 * alphabet but fall within the bounds of the array are translated to -1.
	 */
	private static final byte base64ToInt[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 };

	/**
	 * This array is the analogue of base64ToInt, but for the nonstandard variant that avoids the use of uppercase
	 * alphabetic characters.
	 */
	private static final byte altBase64ToInt[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 22, 23, 24, 25 };

	public static void main( String args[] ) {
		int numRuns = Integer.parseInt( args[0] );
		int numBytes = Integer.parseInt( args[1] );
		java.util.Random rnd = new java.util.Random();
		for ( int i = 0; i < numRuns; i++ ) {
			for ( int j = 0; j < numBytes; j++ ) {
				byte[] arr = new byte[j];
				for ( int k = 0; k < j; k++ )
					arr[k] = (byte) rnd.nextInt();

				String s = byteArrayToBase64( arr );
				byte[] b = base64ToByteArray( s );
				if ( !java.util.Arrays.equals( arr, b ) ) System.out.println( "Dismal failure!" );

				s = byteArrayToAltBase64( arr );
				b = altBase64ToByteArray( s );
				if ( !java.util.Arrays.equals( arr, b ) ) System.out.println( "Alternate dismal failure!" );
			}
		}
	}
}
